1. Technical Field
This disclosure relates generally to video quality evaluation, and, more specifically, to comparing and evaluating video sequences through direct perceptual comparison.
2. Description of the Related Art
Video quality comparison may be performed to ascertain the quality of video imagery by comparing multiple versions of video imagery. For example, video may be evaluated to ascertain differences between a first version of a video and a second version of the same video. For instance, a first version of a video may be encoded or compressed into a second version of the video in such a way as to reduce the amount of memory space necessary to store the video. Such coding may also reduce the amount of bandwidth necessary to transmit the video in a certain amount of time as well as reduce the amount of processing power required to display the video images. Some coding schemes used to compress the video are imperfect and result in perceptible imperfections when the encoded video is decoded and displayed. Video quality comparison may identify such deficiencies. There are multiple ways to evaluate video quality. For example, comparison may be performed by measuring quantitative differences between the encoded and non-coded video data or by discerning qualitative differences through direct visual perception of the displayed video.
Qualitative video comparison may be performed by visual comparison of two versions of a video. For example, a first video may be viewed; then a second video may be viewed subsequently to the first, and visual differences noted. Differences such as visual imperfections (e.g., artifacts, glitches, discoloration) that are apparent in one version but not the other version may be noted. It may be difficult for the person viewing the first and second video to remember characteristics of the first video while viewing the second video. Sometimes the first and second videos are displayed in respective first and second video player windows at once in order to reduce reliance upon the memory of the person viewing the videos. For example, it is known in the art to drag and stretch videos playing in two different players so that they overlap or become somewhat aligned on the screen. This is a delicate, laborious process, and must be done by hand every time a new video is opened for comparison or when a previous video is re-opened. Switching between these manually aligned windows relies on switching operations provided by a general-purpose operating system that interrupt direct visual comparison because they require attention to a menu, or impose a menu or other selection imagery in between comparison images of the videos. Additionally, the multiple controls of the multiple players may hinder synchronous play of the videos, thus nullifying much of the perceived benefit of multiple-window video comparison.